Jatinder Bhatia

Photosensitized Oxidation of Tryptophan and Hepatic Dysfunction in Neonatal Gerbils

Hepatic dysfunction is a common metabolic complication of parenteral nutrition. Studies in animals have suggested that several amino acids, especially tryptophan, may play a role in the development of hepatic dysfunction. Further, photoirradiation of amino acids in the presence of photosensitizers, such as riboflavin, causes photooxidative changes in several amino acids. The present study was undertaken to determine the effect of tryptophan, after photoirradiation in the presence of riboflavin, on hepatic function in neonatal gerbils. Two-week-old suckling gerbils received approximately 4 mmol/kg/day of light-exposed or nonlight-exposed tryptophan or received saline intraperitoneally for 4 days. An increase in the activity of serum gamma-glutamyl transpeptidase was found in gerbils receiving both light-exposed and nonlight-exposed tryptophan compared to control. Concentrations of tryptophan were significantly higher in animals receiving saline than in the other two groups. There were no significant differences in the major tissue amino acids among the three groups of animals. Our data suggest the role of photosensitized oxidation of tryptophan in the pathogenesis of hepatic dysfunction in neonatal gerbils. It is possible that similar photooxidation occurring during infusion of parenteral amino acid solutions containing vitamins exposed to constant illumination in the newborn nursery is responsible for the observed hepatic dysfunction in parenterally fed neonates.

The effects of light exposure on the in vitro hepatic response to an amino acid-vitamin solution.

BACKGROUND Administration of parenteral nutrition (PN) that has been irradiated with light is associated with hepatic dysfunction in rats in vivo. Using the isolated perfused rat liver, we report the in vitro hepatic response to a light-exposed amino acid-vitamin (AAV) solution, compared with a light-protected solution. METHODS The amino acid-vitamin solution (3 g Aminosyn and 2.5 mL MVI-12 added to buffer) was placed under a lamp in a beaker that was covered completely with foil (light-protected) or with a transparent wrap (light-exposed) for 24 hours before liver perfusion. Livers from adult male rats were isolated and perfused with buffer for 30 minutes, with the AAV solution for 60 minutes, and again with buffer for 30 minutes. RESULTS Infusion with the AAV solution resulted in decreases in bile flow rates. Compared with light-protected groups, light-exposure was associated with significantly lower bile flow rates, significant increases in biliary concentrations of oxidized glutathione (GSSG), and significantly decreased biliary concentrations of free amino acids, including the glutathione precursors glutamate and glycine. CONCLUSIONS Perfusion of the isolated rat liver with an AAV solution that has been irradiated with light for 24 hours results in a decrease in bile flow rates and an increase in biliary GSSG concentrations, suggesting oxidant stress. Consideration should be given to protecting solutions from light in the clinical setting.

Two cannula method for parenteral infusion and serial blood sampling in the freely moving rat

Materials and techniques are described for positioning and exteriorizing two chronic venous cannulas in the rat. A cannula for fluid infusion is placed in the inferior vena cava via the femoral vein and exteriorized on the tail, whereas a cannula for blood withdrawal is placed in the superior vena cava and exteriorized in the scapular region. Grooming behavior and range of motion are not impeded since the cannula used for chronic infusion is shielded by a light-weight tail cover instead of a torso harness. Application of this method can minimize numbers of rats used in total parenteral nutrition (TPN) studies as demonstrated by our feasibility study in which serum parameters of liver function were serially monitored in toxin-treated rats infused with nutrient mixtures.

Biliary endogenous inorganic phosphate, D-glucose, IgA and transferrin are differentially altered by hydrostatic pressure

Our objective was to determine the effects of hydrostatic biliary pressure on excretion patterns of endogenous solutes which reflect various pathways of bile formation. A stable in vivo model was developed using anesthetized rats intraduodenally infused with taurocholate to maintain bile flow. Bile was collected during a 2-h basal period, a 4-h pressure period where elevation of the bile duct cannula decreased bile flow to 1/3 the basal rate, and a 2-h period after release of hydrostatic biliary pressure. During pressure treatment, bile salt concentration gradually increased approximately 3-fold, biliary inorganic phosphate concentrations rapidly rose approximately 5-fold, and biliary glucose concentration progressively rose approximately 17-fold. Concentrations of proteins in bile were affected differently with extreme decreases in IgA, moderate decreases in total protein and leucine aminopeptidase, and minimal change in transferrin. By 2 h after pressure release, only the alterations in biliary glucose and IgA persisted. The observed striking and persisting increases in biliary glucose are tentatively explained as an impaired reabsorption of glucose by the biliary tract.

Resolution of pneumothorax in neonates

The resolution time of pneumothorax in neonates requiring tube thoracotomy is not known. We found that 28%, 50%, and 83% of 54 pneumothoraces in 40 neonates resolved within 24, 96, and 168 h of tube thoracotomy, respectively. Pneumothoraces that persisted beyond 168 h were in infants requiring ventilatory assistance. Moreover, a significantly (p < .05) greater number of preterm infants with persistent pneumothorax developed chronic lung disease compared to preterm infants in whom pneumothorax resolved by 168 h.

Glutathione and tissue amino acid responses to light-exposed parenteral nutrients

Effects of infusion of light-exposed (+L) or light-protected (-L) total parenteral nutrition solutions were investigated in rats. The parenteral infusions were carried out for 7 days through jugular cannulas in freely moving rats in metabolic cages. Plasma tyrosine and citrulline, hepatic methionine, valine, isoleucine, leucine and tyrosine, and biliary cystathionine were significantly greater in the -L than +L rats, whereas biliary arginine was significantly lower in the -L compared to +L rats. Bile flow, biliary inorganic phosphate and glucose were significantly lower, whereas biliary total glutathione (GSH+GSSG) was significantly greater in the -L compared to +L animals. These data suggest adverse effects on hepatobiliary function due to light exposure of parenteral nutrients. The endogenous markers used suggest that tight junction permeability, bile acid-independent flow, glutathione and amino acid homeostasis are altered by light exposure and that these changes can be minimized by light protection. The mechanisms involved in the induction of these changes need to be elucidated. The role of light exposure of parenteral nutrients during routine clinical use in the induction of hepatic dysfunction, a common metabolic complication of parenteral nutrition, needs to be considered.

1081 NEONATAL SEPSIS: PREDICTIVE VALUE OF 48 HOUR CULTURE RESULTS

Traditionally, antimicrobial therapy is discontinued in neonates with suspected sepsis when the cultures are reported negative at 72 hours. Rising hospitalization costs and the trend towards early discharge led us to examine the reliability of 48 hour culture results as a guide towards discontinuation of antimicrobial therapy. In a two-part study (Retrospective 69 months; Prospective 2 months), 48 and 72 hour reports of blood and cerebrospinal fluid (CSF) cultures from term neonates were evaluated.The following pathogens were isolated: Group B and D Streptococcus, E. coli, Enterococcus, H. influenzae, and Streptococcus pneumoniae. The single blood culture that was reported positive at 72 hrs but not at 48 hrs was due to H. influenzae; this symptomatic infant received a full course of antibiotics. Discontinuation of antibiotic therapy in clinically well infants based on 48 hr culture results does not appear to compromise quality of medical care and could even facilitate early discharge of term neonates.